A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
In a lithographic apparatus operated in a vacuum environment (e.g. extreme ultraviolet, or EUV, lithography, electron-beam lithography, ion-beam lithography or X-ray lithography), modules (e.g. illumination system, mask table, projection lens or wafer table) of the lithographic apparatus may be separated from each other in different vacuum chambers, due mainly to control negative impacts from contamination. At the same time, these separated chambers are coupled to each other in such a way as to form a lithographic apparatus. Coupling of such chambers may cause issues because each chamber has different tolerances for vibrations (i.e., dynamic noise), normally generated by moving parts in the lithographic apparatus (e.g. mask table or wafer table). To minimize the impact of such vibrations from one chamber to the other, a lithographic apparatus has been separated into a so-called “noisy world” and a so-called “silent world”.
The noisy world in practice may be represented by modules including a base frame dynamically coupled to IC manufacturing factory's floor, which receives all vibrations generated by, for example, operators walking inside such factory.
On the other hand, the silent world may be represented by modules dynamically isolated from the noisy world by employing contact-less supports (e.g. air-foot, air-bearing, magnetic-force levitation, etc) so as to minimize the impact from vibrations generated by any potential sources especially the higher frequency parts of these vibrations (e.g. moving standard deviation parts out from moving average parts).
Vacuum chambers include seals in its opening areas. To minimize the impact of the vibration from the noisy world to the silent world, as disclosed in U.S. Pat. No. 6,333,775 B1 and U.S. Patent Application Publication No. 2006/0007414A1, there is even a contact-less seal introduced. However, it may be difficult to prevent molecular level particles (e.g. hydrocarbon and/or water) from traveling from one chamber to the other by using such a contact-less seal, and if these particles reach the optics in a lithographic apparatus, it may hamper the operation of the optics, as well as contaminate the optics. This may hinder a respective device manufacturing method leading to relatively expensive and/or low-quality devices manufactured thereby.